1. What is the advantage of a camera system that goes beyond RGB and can measure or estimate spectra?

Modern vision and imaging applications rely on interpretation of information acquired by an image sensor. Typically the sensor is designed to emulate human vision, resulting in a color or monochrome image of the field of view as seen by the eye. This is accomplished by sensing light at wavelengths in the visible spectrum (400-700 nm). However, additional information can be gained by creating an image based on the light that is outside the sensitivity of the human eye. The information available can be maximized by combining information found in multiple spectral bands. The photonic spectrum includes energy at wavelengths ranging from the ultraviolet through the visible, near infrared, far infrared, and finally, x-rays. The color image from a Charge Coupled Device (CCD) array is acquired by sensing the wavelengths corresponding to red, green, and blue light.

CCD sensors are capable of detecting light beyond the visible wavelengths out to 1100 nm. The wavelengths from 700 nm to 1100 nm are known as the near infrared (NIR) and are not visible to the eye. In standard color video cameras the infrared light is usually blocked from the CCD sensor because it interferes with the quality of the visible image.

Most imaging systems used in industrial vision and pattern recognition utilize a small number of channels that typically integrate over relatively wide spectral bands. The simplest case is using a black and white camera that captures the gray-scale values of objects - yielding high surface resolution but no spectral information. A color camera, on the other hand, with three image sensors or a sensor with Bayer color filter, will deliver a multi-spectral image with comparably high spatial resolution and three relatively broad-band color channels of red, green and blue, yet with a relatively low spectral resolution. In cases where color accuracy and color control are not important factor these systems tend to work well.

In cases where color accuracy is paramount, the need for multi-spectral imaging exists. Most spectral imaging system operate with just one sensor and a tunable narrow-band filter placed in the optical path to select a frequency. The FD-1665 provides the benefits of a spectral imaging system, but in addition provides high spatial resolution at high frame rates.

2. How does the FD-1665 work?

The standard FD-1665 seven channels are achieved by using two color Bayer arrays and one monochrome array for the near infrared band (NIR). The result is a pair of RGB color images and 1 NIR band equivalent to result in a seven channels in native response.

For customers that need different spectral bands we can provide different prism coatings and trim filter to achieve the required cut-off bands. Please contact us if you have a specific requirement.

3. Why is the FD-1665 different than an ordinary 3CCD camera system?

In addition to the versatility of having any combination of RGB and monochrome sensors and the option of custom filters; the FD-1665 has a patented design that corrects for spherical and chromatic aberration caused by the prism. Below is an overview of the differences between the FD-1665 that uses corrective optics (internal to camera) compared to a standard 3CCD that has no corrective optics.

Patented design to improve chromatic and spherrical aberations caused by typical 3CCD prism cameras

The FD-1665 is designed around a patented design to provided excellent spectral and color quality. The FD-1665 utilizes a patented compensating optics design to provide our 3-CCD cameras to operate over a broad spectral range, 400nm-1000nm while minimizing chromatic and spherical aberrations caused by the prism in standard 3CCD camera systems. The presence of a color separating prism introduces aberrations that degrade the image quality, particularly near the edges of the image, unless something is done to counteract the aberrations.

Typical industrial, machines, and scientific camera systems use standard 35 mm SLR lenses because of the high quality optics, low cost, and large image area. These lenses work very well on 1-CCD cameras. They were never designed for use with a color separating prism.

To evaluate the effect a color separating prism has on image quality, an SLR lens is modeled as an ideal lens and the color separating prism is modeled by a section of glass identical in thickness to the prism. The ray trace for this optical model is shown below. To demonstrate the benefits of our patented compensating optics, the FD-1665 3-CCD camera was modeled and tested.

 

Ray Trace for Camera without Compensating
Optics
 
Zoomed in ray traces of the image plane region are shown below for optics models with compensating optics used in the FD-1665(left) and without compensating optics, typical 3CCD RGB camera (right).  The effects for aberrations are very apparent in the non-compensated model.
 
 
Ray Trace for Showing Trim Filter and Focal Plane
for System with Compensating Optics
Ray Trace Showing Trim Filter and Focal
Plane for System without Compensating Optics

Spot diagrams for the compensated (left) and uncompensated (right) optical models are shown below.

Spot Diagram for System with
Compensating Optics
Spot Diagram for System
without Compensating
Optics

The test setup used to demonstrate the benefits of compensating optics consisted of a single array imaging sensor with a glass element to simulate the presence of a color separating prism. The identical test setup was used for both the compensated and uncompensated images except for the presence of the compensating optics. A Nikon 50 mm focal length, f/1.8 lens was used for the imaging. The image target EIA resolution target. Halogen lamps were used to illuminate the rotating drum. The test camera was filtered with a green filter, simulating the green channel in an RGB 3-CCD prism. The image shown below is one of the images acquired during the test series.

Resolution Chart Imaged

Side-by-side comparisons of the center region and right side of the acquired images are shown below. The images in the left column are for a camera configuration with compensating optics. The images in the left color are for a camera configuration without compensating optics. The lens f-number setting for each image is labeled. The central region of both the compensated and uncompensated test images is quite sharp. It is in the zoomed regions near edge of the test image where significant differences can be observed. The transition from dark-to-light occurs in 2 pixels for the f/4 compensated system. The same dark-to-light transition is spread over 4 pixels in the f/4 uncompensated system. The blurring is primarily in the horizontal direction which is consistent the shapes of the spot diagrams. The blurring effect is even more pronounced when the f/2 images are compared. Images acquired with no optics between the image sensor and 50 mm lens show virtually identical image quality to the compensated optics and prism indicating that with our cameras, image quality is limited by the 35 mm SLR lens and not by the presence of a color separating prism.

Compensating Optics No Compensating Optics
Center Region, f/4 Center Region, f/4
Right Edge, f/4 Right Edge, f/4
Right Edge, f/2 Right Edge, f/2

4. What markets are served by the FD-1665?

The technology based behind the FD-1665 was originally developed for the Art Conservatory Market. Where the interest is in capturing and preserving spectral and color properties of cultural heritage. As a result a wide array of market segments can now benefit from this technology. Examples include:

Application and Segments

 

Market Segment Application
Industrial Vision High Throughput Color Inspection and Verification Systems
Museum Imaging Archiving and Conservation Science
Medical Imaging Iris and Skin Imaging
Food Processing Sorting, inspection and identification of defects
Timber Inspection Classification of species
Textile Color accuracy and consistency in manufacturing
Cosmetics Skin Cosmetics and Dental Imaging
R&D Medical, Government, Defense
Pharmaceutical Tablet Counterfeit Drug Imaging

5. How does the FD-1665 compare to other multi spectral or colorimetric cameras on the markets?

In cases where color accuracy is a deciding factor on what camera system to use, the need for multispectral camera systems arises. There are 2 current configurations that provide spectral images, 1) multi/hyperspectral tunable filter systems and 2) Filter Wheel approach with a monochrome sensor

Comparison of equivalent systems

 

  FD-1665 31 Band Tunable Filter with Monochrome Sensor Filter Wheel Approach with Monochrome Sensor
Size Small Medium Sized Large
Spectral Accuracy High High Medium
Workflow Easy Custom Custom
Noise Low Noise Requires expensive cooled camera for low noise Low Noise
Field of View Large, 18mm -100mm Lens Options Limited by angular dependence of tunable filter Large
Easy of Use Simple Complex Complex
Wavelength Range 400-1000nm 400-700nm 400-700nm
Capture Time Fast Slow Slow
Throughput High Low Low
Pixel Alignment Sub-Pixel Filter Causes shifts

Hard to align

6. What additional software is required to process imagery collected with the FD-1665?

A software development kit (SDK) is provided for users to build their own applications.

7. Why is the product called the FD-1665?

In 1665, Isaac Newton was a young scientist studying at Cambridge University in England. He was very interested in learning all about light and colors. One bright sunny day, Newton darkened his room and made a hole in his window shutter, allowing just one beam of sunlight to enter the room. He then took a glass prism and placed it in the sunbeam. The result was a multicolored band of light just like a rainbow. The multicolored band of light is called a color spectrum.

8. How is the FD-1665 supported?

All of our FluxData products are supported worldwide through our support representatives in Rochester, NY. All hardware and software that is delivered with the system is completed supported by FluxData. FluxData is dedicated in delivering industry leading solutions to customers around the world, and we understand that a healthy part of our success comes from the recognition and appreciation our customers have for our dedicated client support infrastructure.